In addition to the techniques that will help simplify the surge test, this article will also describe some ways to ensure that the defibrillation surge tester works properly during the calibration cycle and is easy to implement.
Energy measurement test The medical electrical equipment international standard IEC60601-1 contains a number of surge tests to ensure that the device under test operates normally under defibrillation pulses. These tests are described in Figures 9, 10 and 11 of IEC 60601-1. Each test requires a 5000V power supply capable of supplying 400 J. The power output on the tester is approximately 360 J (worst case). The three figures in the standard describe different ways of transmitting this pulse to the device under test.
The two methods described in IEC 60601-1:2005 Figures 9 and 10 are the normal mode and differential mode tests, respectively, and can be used to check the separation between the signal input/output components and the patient connection components. A voltage divider network is used to monitor the voltage change of the signal input/output components when the 360-J pulse is applied.
The IEC60601-1 safety standard General Requirements 2005 adds a new energy measurement test that was introduced into this general medical standard from the safety requirements of the IEC60601-2-49 multifunction patient monitoring device. This new requirement states that the instrument connected to the patient can reduce the defibrillation energy delivered through a 100Ω load by up to 10%.
All three of the above tests and other surge tests in the AAMI and IEC medical standards use the 5000-V/400-J engine, except that the waveform components and application technology are different. Because of this similarity, test equipment manufacturers have been able to develop a tester that meets multiple standards at the same time. By looking at the IEC60601 defibrillation tester's documentation, the user can know exactly which standard tests the device can perform; in addition, the connection information for each test method can be viewed.
Figure 1: IEC 60601-1:2005 Figure 9 - Application of test voltage to patient connection in defibrillation application components As shown in the example in Figure 1 (IEC 60601-1:2005 Figure 9), by determining circuit component values ​​and tolerances, the pulses from the 5000-V/400-J power supply can be controlled in the same manner as the IEC/AAMI standard. The area shaded in red in the figure shows the circuitry that the defibrillation surge tester should provide. The circuit in the lower part of the red box area is the universal 5000-V/400-J surge power supply. Below the circuit is a list of components and tolerances; note that all tolerances for surge power supplies are ±5%. Waveform elements vary from standard to standard, but component tolerances for surge power supplies are also ±5%.
Calibration ensures that component tolerance values ​​meet the requirements. For a defibrillation surge tester that is not used or calibrated, the user can be confident that the tolerances are within the above values. However, unless the surge tester is turned on to recheck the component values ​​(which would invalidate the calibration), it is not possible to directly confirm whether the instrument is operating properly during the calibration cycle. Below, we will introduce some ways to check the calibration status without opening the surge tester.
The waveform comparison method IEC 60601-1:2005 uses the defibrillation surge tester (Figures 9, 10, and 11) for all three tests. The pass/fail point is established in the pulse from the 5000-V/400-J power supply. The device under test is based on the transmission. However, if there is no reference data (except for inaccessible component values ​​and tolerances), the power output cannot be confirmed solely based on the information provided in IEC 60601-1:2005. In addition, because the surge tester conforms to IEC 60601-1:2005 requirements only depends on component tolerances, only component tolerances can be verified even if the calibration passes the ISO17025 standard.
Figure 2: IEC60601 display current and its defibrillation waveforms Some manufacturers provide waveforms of the expected output type based on the expected test conditions of the IEC60601-1:2005 standard. If you get these waveforms, it is recommended that you check the output of the new Defibrillation Surge Tester against the generated waveform as follows. If your individual tester does not provide a waveform, consider using the component values ​​given in IEC 60601-1:2005 Figures 9 and 10 (see Figure 2 here) to build an analog waveform. Due to tolerance limitations of the IEC 60601-1:2005 standard, analog waveforms may not accurately model the output of individual defibrillation surge testers. If you do not obtain the desired result when you evaluate the output, you can use the other test methods described in the Accuracy Evaluation section of the Energy Measurement Test below.
Waveform Comparison Test Method This method compares the new waveform generated by the defibrillation surge tester to the waveform in the initial calibration data packet when the instrument is receiving. If there is no such information, the general analog waveform provided in FIG. 2 can be used. This is a simple and quick way to verify the output of a surge tester. Figure 3 shows an example of an initial reference waveform for reference in the test.
The last point: The 5% component tolerances specified by the IEC 60601-1:2005 standard seem to be very strict, but our experience is that some output variations may occur even if all tolerance standards are met. If your defibrillation surge tester output data is not ideal, you can't immediately make a conclusion about the current calibration status of the instrument. Further testing is required. When using a standard defibrillation tester, the output peak voltage will be between 4500V and nearly 5000V due to the different tolerances and qualities of the components used.
1. Use a high voltage high frequency oscilloscope probe. We have achieved very good results using the Tektronix P6015 (available in the secondary market at a reasonable price).
2. Use a digital oscilloscope. The input signal is set to 1.00 kV/vertical division and 500.0 μSec/horizontal division.
3. If your defibrillation surge tester has multiple waveform networks, make sure it is set to 50 ohms, 500 μH.
4. Set the front panel meter to 5000V, indicating that the internal power supply is charged to 5000V (the output will be below this value; see Figure 2 in this article).
5. Start the defibrillation surge tester so that the current is transmitted to the open circuit output and only the high voltage probe is connected.
6. Observe the scope display. The output peak should be between 4500 and 4900V (not 5kV).
7. Find the midpoint of the voltage peak waveform on the waveform duration side. The waveform should conform to the initial waveform and position near 2.42 milliseconds.
8. If the waveform peak or its duration is slightly lower than expected, the defibrillation surge tester may not be able to transmit the required 360J of energy. Further tests should be carried out (see section on evaluation of the accuracy of energy measurement tests below) or maintenance arrangements.
Energy Measurement Test (IEC60601-1,): Resistance Measurement The energy measurement test requires the following two measurements: One reference measurement is used to determine the exact output of the defibrillation surge tester, and the other is to connect the device under test to Defibrillation surge tester output. The difference between the two measurements is within 10% of the pass.
Figure 3: Waveform samples received during detection of the defibrillation surge tester The order of the above tests is very important. The resistance decreases when the resistor is heated. Reduced resistance reduces the energy delivered. This is important because when the device under test is connected to a defibrillation surge tester, the change in resistance due to temperature rise will affect the allowable 10% change in energy. Therefore, it must be ensured that both tests are completed with the same resistance value. Although resistors provided by manufacturers of defibrillation surge testers are used in accordance with the recommended work cycle, the change in resistance does not exceed 5% of the nominal value, but resistance measurement between two tests is still recommended. The time at which the resistor returns to the initial resistance value used in the reference test may exceed the manufacturer's published duty cycle time.
Energy Measurement Test: Resistance Measurement 1. Before performing the energy measurement test, discharge the resistance with a cold resistance of 100Ω into the defibrillation surge tester.
2. Make sure the defibrillation surge tester is not charged. Follow the manufacturer's prescribed procedures to ensure that this requirement is met. Normally, the instrument should be started and the front panel voltmeter reading should be close to 0 volts.
3. Turn off the defibrillation surge tester.
4. Place the ohmmeter between the energy measurement port and the defibrillation surge tester ground wire. The measured value should be within ± 5% of 100Ω.
5. Perform energy measurement reference test; that is, according to IEC60601-1:2005 standard, no instrument is connected to the output of the defibrillation surge tester. Confirm the output energy and record the result.
6. Repeat steps 2 and 3 above.
7. Place the ohmmeter between the energy measurement port and the defibrillation surge tester ground wire. If the value is slightly lower than the measured value in step 4, wait for the resistor block to cool so that the value is close to the measured value in step 4.
8. Connect the device under test to the defibrillation surge tester and perform an energy measurement test. A difference of less than 10% between the above two results is acceptable.
Energy Measurement Test (IEC 60601-1 Figure 11): Accuracy Evaluation If your Defibrillation Surge Tester is already available for IEC 60601-1:2005 testing, it can be equipped with an energy port for testing as shown in Figure 11. This port can also be used to confirm the exact energy output of the defibrillation surge tester. When using a 5000-V power supply and a 32-μF capacitor, the output energy of any test should be higher than 360J (see Figure 1 herein). The method of operation of this reference test is the same as the first part of the energy measurement test. Since the method of transferring waveform data from an oscilloscope to an Excel spreadsheet differs depending on the oscilloscope used, the following is only a brief operation flow. In addition, users can also obtain a free form from our website. A URL link is provided at the end of the article.
Energy Measurement Test Summary Procedure 1. Remove the load from the defibrillation surge tester output.
2. If necessary, set the defibrillation surge tester to 25-mH, 400-Ω.
3. Measure the resistance of the 100-Ω resistor using the above resistance measurement method.
4. Using an appropriate high-voltage probe (for example, Tektronix P6015), connect the oscilloscope to both ends of the 100-Ω resistor row inside the tester. For most testers, this position is between the energy measurement output and the tester ground.
5. Use a digital oscilloscope that can transfer waveform data to an Excel spreadsheet. Set up the oscilloscope to capture the entire waveform. Set the vertical axis to 1000V/div and the horizontal axis to 2msec/div.
6. Charge the defibrillation surge tester until its internal power supply is charged to 5000V. (In most cases, the power voltage is displayed on the front panel display.) Then, start the defibrillation surge tester.
7. The display should show the complete oscilloscope waveform, starting from 0V and ending at 0V. Visit the URL http://Products/Downloads/Energy_calculation_TUV_EC13_10.75ohm_open.xls to see the ideal waveform diagram included in the Excel spreadsheet. If you do not get a complete waveform when using the recommended settings, adjust the settings until the oscilloscope display shows the complete waveform.
8. Transfer the waveform data to an Excel spreadsheet. The method of operation for this step depends on the oscilloscope type used.
9. Open the Excel spreadsheet. Delete waveform data outside the start and end of the waveform. (The noise components of these data can lead to large energy results.)
10. Calculate the result using an Excel spreadsheet. The result should be higher than 360J.
If the result is significantly lower than 360J, check the defibrillation surge tester to correct the cause of the low output energy.
Defibrillation Prevention Test (IEC60601-1 Figures 9 and 10): Accuracy Assessment All of the above methods and discussions related to the power supply of the defibrillation surge tester. A laboratory that follows these guidelines should ensure that the tester is operating properly and that it is suitable for energy measurement tests. However, for the normal mode and differential tests shown in Figures 9 and 10 of IEC 60601-1:2005, it must also be ensured that the voltage divider network is operating normally (as shown in the upper part of the red band in Figure 1).
One way to perform this verification is to replace the instrument under test with a known value, that is, instead of all the white parts in Figure 1 herein. This is the most effective verification method; in addition, if you get the expected output value, you can also prove that the entire test setup is correct.
Some manufacturers provide defibrillation pass/fail measurement tools that can be inserted into the above test setup. This pass/fail measurement tool is shipped from the factory with a specific Defibrillation Surge Tester because the same settings cannot be used for all testers according to the IEC 60601-1:2005 tolerance specification. However, uncalibrated pass/fail measurement tools can still be used if necessary to obtain useful information while verifying the test setup and the overall integrity of the defibrillation surge tester.
Conclusion This article introduced the new surge test in the IEC 60601-1:2005 standard and introduced some processes and recommendations to simplify testing and ensure correct test results. In addition, this article describes some simple ways to ensure that your defibrillation surge tester works properly between calibration cycles. These methods can be used to understand the overall condition of the defibrillation tester and ensure that the tester connection is valid. We hope that these methods will help ensure that all tests are completed when the equipment is working well.
Energy measurement test The medical electrical equipment international standard IEC60601-1 contains a number of surge tests to ensure that the device under test operates normally under defibrillation pulses. These tests are described in Figures 9, 10 and 11 of IEC 60601-1. Each test requires a 5000V power supply capable of supplying 400 J. The power output on the tester is approximately 360 J (worst case). The three figures in the standard describe different ways of transmitting this pulse to the device under test.
The two methods described in IEC 60601-1:2005 Figures 9 and 10 are the normal mode and differential mode tests, respectively, and can be used to check the separation between the signal input/output components and the patient connection components. A voltage divider network is used to monitor the voltage change of the signal input/output components when the 360-J pulse is applied.
The IEC60601-1 safety standard General Requirements 2005 adds a new energy measurement test that was introduced into this general medical standard from the safety requirements of the IEC60601-2-49 multifunction patient monitoring device. This new requirement states that the instrument connected to the patient can reduce the defibrillation energy delivered through a 100Ω load by up to 10%.
All three of the above tests and other surge tests in the AAMI and IEC medical standards use the 5000-V/400-J engine, except that the waveform components and application technology are different. Because of this similarity, test equipment manufacturers have been able to develop a tester that meets multiple standards at the same time. By looking at the IEC60601 defibrillation tester's documentation, the user can know exactly which standard tests the device can perform; in addition, the connection information for each test method can be viewed.
Figure 1: IEC 60601-1:2005 Figure 9 - Application of test voltage to patient connection in defibrillation application components
Calibration ensures that component tolerance values ​​meet the requirements. For a defibrillation surge tester that is not used or calibrated, the user can be confident that the tolerances are within the above values. However, unless the surge tester is turned on to recheck the component values ​​(which would invalidate the calibration), it is not possible to directly confirm whether the instrument is operating properly during the calibration cycle. Below, we will introduce some ways to check the calibration status without opening the surge tester.
The waveform comparison method IEC 60601-1:2005 uses the defibrillation surge tester (Figures 9, 10, and 11) for all three tests. The pass/fail point is established in the pulse from the 5000-V/400-J power supply. The device under test is based on the transmission. However, if there is no reference data (except for inaccessible component values ​​and tolerances), the power output cannot be confirmed solely based on the information provided in IEC 60601-1:2005. In addition, because the surge tester conforms to IEC 60601-1:2005 requirements only depends on component tolerances, only component tolerances can be verified even if the calibration passes the ISO17025 standard.
Figure 2: IEC60601 display current and its defibrillation waveforms
Waveform Comparison Test Method This method compares the new waveform generated by the defibrillation surge tester to the waveform in the initial calibration data packet when the instrument is receiving. If there is no such information, the general analog waveform provided in FIG. 2 can be used. This is a simple and quick way to verify the output of a surge tester. Figure 3 shows an example of an initial reference waveform for reference in the test.
The last point: The 5% component tolerances specified by the IEC 60601-1:2005 standard seem to be very strict, but our experience is that some output variations may occur even if all tolerance standards are met. If your defibrillation surge tester output data is not ideal, you can't immediately make a conclusion about the current calibration status of the instrument. Further testing is required. When using a standard defibrillation tester, the output peak voltage will be between 4500V and nearly 5000V due to the different tolerances and qualities of the components used.
1. Use a high voltage high frequency oscilloscope probe. We have achieved very good results using the Tektronix P6015 (available in the secondary market at a reasonable price).
2. Use a digital oscilloscope. The input signal is set to 1.00 kV/vertical division and 500.0 μSec/horizontal division.
3. If your defibrillation surge tester has multiple waveform networks, make sure it is set to 50 ohms, 500 μH.
4. Set the front panel meter to 5000V, indicating that the internal power supply is charged to 5000V (the output will be below this value; see Figure 2 in this article).
5. Start the defibrillation surge tester so that the current is transmitted to the open circuit output and only the high voltage probe is connected.
6. Observe the scope display. The output peak should be between 4500 and 4900V (not 5kV).
7. Find the midpoint of the voltage peak waveform on the waveform duration side. The waveform should conform to the initial waveform and position near 2.42 milliseconds.
8. If the waveform peak or its duration is slightly lower than expected, the defibrillation surge tester may not be able to transmit the required 360J of energy. Further tests should be carried out (see section on evaluation of the accuracy of energy measurement tests below) or maintenance arrangements.
Energy Measurement Test (IEC60601-1,): Resistance Measurement The energy measurement test requires the following two measurements: One reference measurement is used to determine the exact output of the defibrillation surge tester, and the other is to connect the device under test to Defibrillation surge tester output. The difference between the two measurements is within 10% of the pass.
Figure 3: Waveform samples received during detection of the defibrillation surge tester
Energy Measurement Test: Resistance Measurement 1. Before performing the energy measurement test, discharge the resistance with a cold resistance of 100Ω into the defibrillation surge tester.
2. Make sure the defibrillation surge tester is not charged. Follow the manufacturer's prescribed procedures to ensure that this requirement is met. Normally, the instrument should be started and the front panel voltmeter reading should be close to 0 volts.
3. Turn off the defibrillation surge tester.
4. Place the ohmmeter between the energy measurement port and the defibrillation surge tester ground wire. The measured value should be within ± 5% of 100Ω.
5. Perform energy measurement reference test; that is, according to IEC60601-1:2005 standard, no instrument is connected to the output of the defibrillation surge tester. Confirm the output energy and record the result.
6. Repeat steps 2 and 3 above.
7. Place the ohmmeter between the energy measurement port and the defibrillation surge tester ground wire. If the value is slightly lower than the measured value in step 4, wait for the resistor block to cool so that the value is close to the measured value in step 4.
8. Connect the device under test to the defibrillation surge tester and perform an energy measurement test. A difference of less than 10% between the above two results is acceptable.
Energy Measurement Test (IEC 60601-1 Figure 11): Accuracy Evaluation If your Defibrillation Surge Tester is already available for IEC 60601-1:2005 testing, it can be equipped with an energy port for testing as shown in Figure 11. This port can also be used to confirm the exact energy output of the defibrillation surge tester. When using a 5000-V power supply and a 32-μF capacitor, the output energy of any test should be higher than 360J (see Figure 1 herein). The method of operation of this reference test is the same as the first part of the energy measurement test. Since the method of transferring waveform data from an oscilloscope to an Excel spreadsheet differs depending on the oscilloscope used, the following is only a brief operation flow. In addition, users can also obtain a free form from our website. A URL link is provided at the end of the article.
Energy Measurement Test Summary Procedure 1. Remove the load from the defibrillation surge tester output.
2. If necessary, set the defibrillation surge tester to 25-mH, 400-Ω.
3. Measure the resistance of the 100-Ω resistor using the above resistance measurement method.
4. Using an appropriate high-voltage probe (for example, Tektronix P6015), connect the oscilloscope to both ends of the 100-Ω resistor row inside the tester. For most testers, this position is between the energy measurement output and the tester ground.
5. Use a digital oscilloscope that can transfer waveform data to an Excel spreadsheet. Set up the oscilloscope to capture the entire waveform. Set the vertical axis to 1000V/div and the horizontal axis to 2msec/div.
6. Charge the defibrillation surge tester until its internal power supply is charged to 5000V. (In most cases, the power voltage is displayed on the front panel display.) Then, start the defibrillation surge tester.
7. The display should show the complete oscilloscope waveform, starting from 0V and ending at 0V. Visit the URL http://Products/Downloads/Energy_calculation_TUV_EC13_10.75ohm_open.xls to see the ideal waveform diagram included in the Excel spreadsheet. If you do not get a complete waveform when using the recommended settings, adjust the settings until the oscilloscope display shows the complete waveform.
8. Transfer the waveform data to an Excel spreadsheet. The method of operation for this step depends on the oscilloscope type used.
9. Open the Excel spreadsheet. Delete waveform data outside the start and end of the waveform. (The noise components of these data can lead to large energy results.)
10. Calculate the result using an Excel spreadsheet. The result should be higher than 360J.
If the result is significantly lower than 360J, check the defibrillation surge tester to correct the cause of the low output energy.
Defibrillation Prevention Test (IEC60601-1 Figures 9 and 10): Accuracy Assessment All of the above methods and discussions related to the power supply of the defibrillation surge tester. A laboratory that follows these guidelines should ensure that the tester is operating properly and that it is suitable for energy measurement tests. However, for the normal mode and differential tests shown in Figures 9 and 10 of IEC 60601-1:2005, it must also be ensured that the voltage divider network is operating normally (as shown in the upper part of the red band in Figure 1).
One way to perform this verification is to replace the instrument under test with a known value, that is, instead of all the white parts in Figure 1 herein. This is the most effective verification method; in addition, if you get the expected output value, you can also prove that the entire test setup is correct.
Some manufacturers provide defibrillation pass/fail measurement tools that can be inserted into the above test setup. This pass/fail measurement tool is shipped from the factory with a specific Defibrillation Surge Tester because the same settings cannot be used for all testers according to the IEC 60601-1:2005 tolerance specification. However, uncalibrated pass/fail measurement tools can still be used if necessary to obtain useful information while verifying the test setup and the overall integrity of the defibrillation surge tester.
Conclusion This article introduced the new surge test in the IEC 60601-1:2005 standard and introduced some processes and recommendations to simplify testing and ensure correct test results. In addition, this article describes some simple ways to ensure that your defibrillation surge tester works properly between calibration cycles. These methods can be used to understand the overall condition of the defibrillation tester and ensure that the tester connection is valid. We hope that these methods will help ensure that all tests are completed when the equipment is working well.
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